Abstract The coherent superposition of beamlets with proper frequency shift, spatial phase difference and polarization control can smooth the irradiation uniformity and rotate the polarization of focal spot on picosecond timescale. In our previous work, the introduction of spatial phase difference requires insertion of additional phase plates that might increase the laser cost and complexity. In this paper, we propose a simple method to introduce the required spatial phase difference without inserting any additional optical elements in the beamline, but good-working in improving irradiation uniformity and rotating polarization of the focal spot. This novel method takes full advantages of continuous phase plate to explore its potential in introducing the spatial phase difference among beamlets. Two representative approaches have been presented, i.e., the first is designing individual CPP for each beamlet which can generate focal spot with same intensity envelope but different speckles individually, and the second is mounting the identical CPP for each beamlet in different orientations. Results indicate that, this simple method can effectively improve the irradiation uniformity within the sub-picosecond timescale and bring about polarization rotation to suppress the parametric backscattering.

中文翻译：

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一种通过空间相位差干涉小波束实现超快平滑和偏振旋转的简单方法

摘要 具有适当频移、空间相位差和偏振控制的小束相干叠加可以平滑辐照均匀性并在皮秒时间尺度上旋转焦斑的偏振。在我们之前的工作中，空间相位差的引入需要插入额外的相位板，这可能会增加激光器的成本和复杂性。在本文中，我们提出了一种简单的方法来引入所需的空间相位差，而无需在光束线中插入任何额外的光学元件，但在改善辐照均匀性和焦斑旋转偏振方面效果良好。这种新方法充分利用了连续相位板的优点，探索了其在小束之间引入空间相位差的潜力。已经提出了两种具有代表性的方法，即 ，第一个是为每个小束设计单独的 CPP，可以生成具有相同强度包络但单独散斑不同的焦斑，第二个是在不同方向为每个小束安装相同的 CPP。结果表明，这种简单的方法可以有效地提高亚皮秒时间尺度内的辐照均匀性，并通过偏振旋转来抑制参数背向散射。